the notifications you are seeing are coming from a calendar, but one that you normally should not be able to see. From the appointment names this seems to be the folder that you have set as HIDDEN_FOLDERNAME in gabsync.conf.php.

Did you change this folder from the default and used an already existing folder for this?

The feature introduced with KOE 1.3 to suppress reminders in shared calendars has only been implemented for calendar folders, so if you set a reminder on an email this still could come up (but this is not what your screenshot shows).

Subfolders in your account? We have seen this from time to time already in Outlook. Outlook gets into a kind of resync loop which has as a side effect, that only some folders still show up on the client. To fix this you currently still have to close Outlook and then delete the used ost file. On the next start Outlook will then completely resync your data and the subfolders should be there again.

I had a small chat with the KOE developer over this. Currently its actually the case that we ignore reminders from all shared folders, and optionally allow reminders from calendars. I have created a followup ticket to automatically suppress reminders from the gab folder as well.